Gas log heaters which burn gas and which utilize artificial logs to simulate the appearance of burning wood logs are known in the art. Such heaters may be in form of a fireplace insert or a free-standing heater having a window for viewing the artificial logs. The heaters typically include several artificial logs of a ceramic or other refractory material designed to simulate the appearance of wood logs. A gas burner supplies a mixture of a flammable gas and air underneath the artificial logs. The gas is burned to produce a flame in the vicinity of the logs. The heater can include a tank or reservoir for holding the flammable gas, or can be connected to a remote gas source. Heaters utilizing artificial log assemblies provide heat and the pleasing appearance of a wood fire, while avoiding the inconvenience and lack of cleanliness associated with the loading of wood into and removal of ashes from conventional wood burning stoves and fireplaces.
One objective in the design and construction of gas log heaters is to provide artificial logs that look like real logs and to provide gas flames which closely simulate the flames produced by burning wood, so that an overall effect of burning wood is produced. The size and color of the flames and their positions relative to the artificial logs are important in producing a realistic effect. Other important objectives in the design and construction of gas log heaters include providing high heat output, providing high combustion efficiency, minimizing the soot and noxious gases produced by combustion and minimizing the cost of the heater.
The design of the gas burner is important in producing flames which simulate those of burning wood logs and in controlling emissions of noxious gases, such as carbon monoxide. One type of prior art gas burner, known as a tube burner, employs a pipe that is closed at one end and is connected to a gas source at the other end. The pipe includes a series of spaced holes which supply gas in the region of the artificial logs. Examples of tube type gas burners are disclosed in U.S. Pat. Nos. 3,362,395 issued Jan. 9, 1968 to Peterson; 3,042,109 issued Jul. 3, 1962 to Peterson; 3,871,355 issued Mar. 18, 1975 to Henry; 3,543,741 issued Dec. 1, 1970 to Whitehead; and 3,760,790 issued Sep. 25, 1973 to Voges et al. The disclosed gas burners are relatively low in cost and can be operated with high efficiency. However, these burners typically produce a row of steady blue flames which are not effective in simulating burning wood logs.
A gas burner fabricated of a refractory fiber material is disclosed in U.K. Patent No. 2,156,507, published Oct. 9, 1985. A gas log fireplace utilizing a ceramic gas burner fabricated of a refractory fiber material is disclosed in U.S. Pat. No. 5,092,313 issued Mar. 3, 1992 to Blackburn et al. The ceramic gas burner includes a refractory fiber insulating body having a plurality of front and top ports, a Venturi tube inlet for receiving a combustible gas and primary air, and an interior chamber connecting the inlet to the front ports and to the top ports. The ceramic gas burner is effective, in combination with artificial logs, in simulating a wood fire. However, the ceramic gas burner is difficult to manufacture and may be subject to damage during use. Furthermore, the ceramic gas burner does not meet recently-imposed standards for carbon monoxide emissions, requires on the order of 15-20 minutes to reach steady state combustion, and is occasionally subject to flashback into the burner cavity when the gas is turned off.
Additional gas burner and artificial log assemblies are disclosed in U.S. Pat. No. 4,306,537 issued Dec. 22, 1981 to Mitchell, U.S. Pat. No. 4,886,445 issued Dec. 12, 1989 to Richardson and U.K. Patent Application Nos. 2,208,703 (Izzard); 2,185,100 (Wright); and 2,179,438 (Bleach). All known prior art gas log heaters have had one or more disadvantages, including an unrealistic appearance, low combustion efficiency, lack of reliability and durability, unacceptable emissions of noxious gases and difficulties in manufacturing.